The present invention generally relates to a paper feeder for use in a copying machine or a printing machine and, more particularly, to a paper feeder of a type comprising at least two supply units for the support or storage of recording materials such as papers, which supply units are alternately brought into operation one at a time when the recording material contained in one of the supply units has been used and if the recording materials respectively contained in the supply units are of the same size.
To those who are concerned with the manufacture of electrophotographic copying machines or printing machines, there is well known a paper feeder of a type comprising at least two supply units for the support or storage of recording materials each being in the form of a batch of papers of equal size, which supply units are selectively brought into operation one at a time. In this known paper feeder, the supply units are so designed as to accommodate respective recording materials of different size, and it is considered convenient in that, when copying or printing is desired to be effected on the recording material of a size different from that previously used, an appropriate supply unit can be brought into operation to cope with the desire. This is in contrast to the paper feeder comprising a single supply unit which requires occassional replacement of the recording material of one particular size with that of a different size.
However, so far as the capability of successive feeding of papers of one particular size is involved, there is no difference in performance between the paper feeder of the type having at least two supply units and that having only one supply unit. This is because one supply unit operates independently of the other supply unit and the two are not operatively associated with each other. This equally applies even in the case where at least one of the supply units is so adjustably designed as to accommodate the recording material of a size equal to that accommodated in the other of the supply units. Therefore, when two batches of papers of equal sizes are placed in the respective supply units to enable the paper feeder to supply a relatively large number of papers in excess of the number of the papers of one batch accommodated in one supply unit, a manual intervention is required when one batch of papers in one of the supply units have completely been consumed, so that the other of the supply units can be brought into operation.
In particular, when an electrophotographic copying machine having the paper feeder of the above described type incorporated therein is used, it has often been experienced that, in view of the fact that the number of papers of two batches of equal or different sizes remaining in the respective supply units is not known to an operator of the copying machine, the paper feeder will supply no paper from one of the supply units when the papers contained in such one of the supply units have completely been consumed and, in such case, the operator is required to manipulate a switching mechanism to bring the other of the supply units into operation if such other of the supply units has contained a batch of papers equal in size to that of the consumed papers or to replenish the empty supply unit with a fresh batch of papers of a size equal to that of the consumed papers.
However, the Japanese Patent Laid-open Publication No. 52-25639, laid open to public inspection on Feb. 25, 1977, discloses a similar paper feeder for use in a copying machine which substantially obviates the above described disadvantages and inconveniences. This prior art paper feeder disclosed in the above mentioned publication comprises at least first and second trays positioned one above the other for the support of respective first and second containers, containing therein respective batches of copying papers, which may be either equal or different in size; first and second feed rolls operatively associated with the respective first and second trays, any one of the first and second feed rolls being, when the container on the corresponding tray is filled with the copying papers, brought into contact with the top of the copying papers for feeding the latter from the corresponding container on the corresponding tray towards a processing station during rotation thereof; a first drive control including a first electromagnetic clutch which is, when the first drive control is activated, engaged to allow the first feed roll to be driven in one direction; a second drive control including a second electromagnetic clutch which is, when the second drive control is activated, engaged to allow the second feed roll to be driven in one direction; a size selector switch having a movable contact electrically connected to a power source and first and second fixed contacts respectively electrically connected to the first and second drive controls; a size detector positioned between the power source and any one of the first and second drive controls for detecting whether or not the size of the container placed on the first tray is equal to that placed on the second tray and operable to allow the passage of an electric power from the power source therethrough only when the containers on the respective first and second trays and, therefore, the copying papers in the associated containers, are equal in size to each other; means operable by the electric power fed through the size detector to interrupt the supply of the electric power from the power source to any one of the first and second drive controls through the size selector switch; a first paper detector means, including a first relay switch disposed on an electric circuit between the first drive control and the size detector, for detecting whether or not the container on the first tray is filled with the copying papers and for causing the first relay switch to close only during the presence of the copying papers in the container on the first tray whereby, so long as the interrupting means is held in position to interrupt the supply of the electric power from the power source to any one of the first and second drive controls through the size selector switch due to the presence of the copying papers of the two batches of equal size in the containers respectively placed on the first and second trays, the first drive control can be activated by the electric power fed through the size detector; and a second paper detector means including a second relay switch and operable only when and so long as the first paper detector means is brought in an inoperative position due to complete consumption of the copying papers from the container on the first tray, for detecting whether or not the container on the second tray is filled with the copying papers and for causing the second relay switch to close only during the presence of the copying papers in the container on the second tray and the absence of the copying papers in the container on the first tray whereby, so long as the interrupting means is held in position to interrupt the supply of the electric power from the power source to any one of the first and second drive controls through the size selector switch due to the presence of the copying papers of the two batches of equal size in the containers respectively placed on the first and second trays, the second drive control can be activated by the electric power fed through the size detector.
The prior art paper feeder disclosed in the above mentioned publication further comprises a first indicator lamp energizable during the engagement of the first drive control to show that the first tray is in an operative position with the papers in the container on the first tray being fed by the first feed roll towards the processing station, and a second indicator lamp energizable during the engagement of the second drive control to show that the second tray is in an operative position with the papers in the container on the second tray being fed by the second feed roll towards the processing station.
In summary, the prior art paper feeder of the construction described above is so designed that, when and so long as the identical containers containing the respective batches of copying papers of equal size are placed on the associated first and second trays, the first drive control is activated to cause the first electromagnetic clutch to be engaged to drive the first feed roll and the second drive control is subsequently activated to cause the second electromagnetic clutch to be engaged to drive the second feed roll while the first drive control is inactivated when and after the copying papers in the container on the first tray have been consumed. Yet, after the copying papers in the container on the first tray have completely been consumed and it has subsequently been replenished with a fresh batch of copying papers of equal size during the copying papers being fed out of the container on the second tray, the second drive control is immediately inactivated while the first drive control is activated before the copying papers in the container on the second tray are completely consumed. However, after the copying papers in the container on the first tray have completely been consumed and it has subsequently been replenished with a fresh batch of copying papers of a size different from that previously consumed, the size detector is held in position to interrupt the supply of the electric power therethrough to any one of the first and second drive controls, but completing the circuit between the power source and the movable contact of the manipulatable size selector switch and, depending upon the position of the movable contact of the size selector switch, there is the possibility that, in the course of reproduction of information on the copying papers of equal size, that information will be reproduced on one or more copying papers of a size different from that of the previously used copying papers.